Skin Cancer and Sun Sense

by Food and Drug Administration (FDA)

"This looks like skin cancer," the dermatologist told the woman as he examined the spot on her leg. Later, after removing the tumor and several other precancerous growths from her face and hands, he looked her in the eyes and said, "You've had enough sun."

More and more people are hearing similar messages from their doctors. Viewed as an undeclared epidemic by dermatologists, skin cancer is the most prevalent of all cancers, and it's increasingly common. About a million Americans will develop skin cancer this year.

"Skin cancer is now about as common as all other cancers combined," says Martin A. Weinstock, M.D., Ph.D., director of Brown University's Dermatoepidemiology Unit and Chief of Dermatology at the Providence (R.I.) Veterans Affairs Medical Center. And there's no evidence that the epidemic has peaked.

But there is a bright side. Skin cancer is quite curable when treated early. More than 90 percent of skin cancers are completely cured. Even better, it's largely preventable, simply by avoiding sun and sunlamp exposure.

As more consumers become sun smart, they're finding new ways to protect themselves. For example, FDA has cleared for marketing one manufacturer's clothing for sun protection. Eating a healthier diet can't hurt — less fat, more fruits, vegetables and grains — and preliminary studies indicate it may help. And the National Weather Service provides a measure of ultraviolet (UV) exposure with its UV Index, which is part of the daily weather forecast for many cities.

Experts agree that sunlight, particularly the UV wavelengths, damages the skin. UV radiation causes the obvious short-term damage seen in a sunburn or a tan, as well as the long-term damage that accumulates with each exposure. Not only is there no such thing as a safe tan, "There's no known safe amount of sun," Weinstock says.

Americans are getting the message. Increasingly, we're protecting ourselves from the sun, according to a 1994 survey commissioned by the American Academy of Dermatology. But we're not all sun savvy yet. Only 2 in 5 people consistently use sunscreen whenever they're in the sun. Fewer people say they sunbathe, but about 1 in 5 adults still does. And some people have the mistaken impression that sunlamps or tanning salons are somehow better or safer than natural sunlight. They aren't. No matter what the source, UV exposure increases your risk of skin cancer. (See "Sunlamps — Not a Bright Idea.")

There are three main types of skin cancer. Melanoma is the least common but most serious because this killer is responsible for three-quarters of the nearly 10,000 skin cancer deaths per year. The other two types — basal cell and squamous cell carcinomas — are often referred to together as non-melanoma skin cancer. Basal cell cancer is by far the most common skin cancer, followed by squamous cell carcinoma, which can also become a killer. Between 1980 and 1989, the incidence of non-melanoma skin cancers increased 65 percent, and melanoma 21 percent. And skin cancer is striking at ever younger ages. One-quarter of the more than 30,000 people expected to develop melanoma this year will be 39 or younger.

A fourth type of growth, actinic or solar keratosis, is also of concern because it can progress into cancer. It's the most common pre-malignant skin condition, occurring in more than 5 million Americans.

UV's Double Whammy

While there's no question that UV damages DNA, scientists had long suspected that it delivers a double whammy. Recent research supports that idea. Developing skin cancer is at least a two-step process, involving initiation and promotion of malignant growth. "UV plays both roles," says Douglas Brash, Ph.D., a biophysicist at Yale University School of Medicine. In studies with mice, Brash and colleagues showed that UV harms a mechanism for repairing cell damage. Once the repair system is impaired, cells become increasingly vulnerable to injury. Subsequent UV exposures just make matters worse, and can initiate malignancy.

After UV exposure, the repair mechanism normally directs damaged cells to commit suicide. That's why skin peels after a sunburn. "It's a mop-up operation," says Brash. But previously damaged cells with a malfunctioning repair system escape this mop up. Genetic damage accumulates as normal cells die and abnormal ones survive.

Brash said the level of UV used in their experiments was about equivalent to exposure from a day at the beach. Skin doesn't have to be badly sunburned, he said, adding that such damage also accumulates with chronic, everyday exposure.

To increase awareness of the damaging potential of UV radiation, the Environmental Protection Agency and the National Weather Service developed the UV Index. Besides skin cancer, UV radiation also increases the risk of cataracts and certain other eye problems, and can suppress the immune system. And although dark-skinned people are generally less likely to get skin cancer than light-skinned people, they are just as susceptible to cataracts or immune suppression.

The UV Index number, ranging from 0 to 10+, indicates the amount of UV radiation reaching the Earth's surface during an hour around noon. (See "UV or not UV.") It's forecast daily for 58 cities, based on local predicted conditions. The UV Index is valid only for about a 30-mile radius from the city, and, as with any forecast, local variability in cloud cover and other factors may change actual levels experienced. But it serves as a reminder to take precautions against UV exposure.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.